Original message
| fil
 |  "heil sp80 does not reach target temp"
, posted Sun 13 Jan 03:37  
The furnace works, but (especially on cold days) does not reach set target temperature (e.g., 70F). At some point it turns off burners, only exhaust fan keeps working, after a while the burners kick back in, works for a few minutes then turns burners off and so on. Since it can not reach the target temp exhaust fan never goes off. Could it be that one of the sensors is failing? Checked the pressure switch, seems to be fine. All vents are open, it should not be overheating. Looking for a manual to understand the sequence. Any advice much appreciated.
Alex
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Replies:
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| dwcaveney
| "Re(1):heil sp80 does not reach target temp" , posted Sun 13 Jan 04:03:
Do your t-stat wires run through CAR duct? Chicago Industries makes a good t-stat (check it out). Other wise buy a Honeywell. Might need to pack an extra wire, and/or permanently modify ductwork.
[this message was edited by dwcaveney on Sun 13 Jan 04:15] |
| | fil
| "Re(2):heil sp80 does not reach target temp" , posted Mon 14 Jan 21:18
I do not know much about furnace troubleshooting, could you explain how the fact that "t-stat wires run through CAR duct" might cause the symptoms described?
Alex
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| tinmantu
| "Re(1):heil sp80 does not reach target temp" , posted Sun 13 Jan 03:58
if your burners are dropping out before set temp. is reached, the first step is to check temp. across return and supply at the furnace...if it's greater than 60 degrees, you have problems that need to be looked at by a professional. Putting a volt meter on the high limit and observing when burners drop out will confirm, after doing the temp check.
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| | fil
| "Re(2):heil sp80 does not reach target temp" , posted Mon 14 Jan 21:25
I found manual for my electronic fan timer
http://customer.honeywell.com/techlit/pdf/PackedLit/69-0644.pdf
Fig. 2 describes my setup (with SmartValve).
>Putting a volt meter on the high limit
Where would you suggest attaching the voltmeter to check temp?
Alex
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| | yuri
| "Re(2):heil sp80 does not reach target temp" , posted Sun 13 Jan 10:43
I would get a pro to check that unit. Unfortunately LOTS of them have cracked heat exchangers/popped compression rings.
Yuri
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| | fil
| "Re(3):heil sp80 does not reach target temp" , posted Mon 14 Jan 21:29
A tech who was cleaning the unit suggested to replace the control board, but could not give any explanation. Cracked heat exchanger sounds scary.
>cracked heat exchangers/popped compression rings
How would this explain what is happening to my unit?
Thanks
Alex
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